Forodesine in presence of dGuo lowered the GTP and ATP levels in CLL cells, while the same NTPs increased when cocultured with MSCs. CLL cells (n = 5) were incubated without or with 2μM forodesine and 20μM dGuo in suspension or on MSCs for 24 hours (A,C) or 48 hours (B,D), and the levels of GTP (A-B) and ATP (C-D) were measured by HPLC. C indicates CLL; F, forodesine plus dGuo; M, M210B4; and N, NKtert.